Cell surface markers permit the identification of cellular phenotypes characteristic of both healthy and disease states, e.g. Maecker et al, J. Clin. Immunol., 20: 391-399 (2000); Rothe et al, Leukemia, 10: 877-895 (1996); Reilly et al, J. Clin. Pathol., 54: 508-511 (2001). Such markers are typically measured by staining a cell sample with a selection of labeled antibodies specific for different markers, followed by multi-parameter analysis by imaging or by flow cytometry, e.g. Stewart, Immunophenotyping (Wiley-Liss, 2000). Multi-parameter analysis using labeled antibodies, or immunophenotyping, has been particularly useful for identifying distinct functional and developmental classes of white blood cells, which has important applications in the classification of blood-related diseases, such as leukemias and lymphomas, and in the monitoring the status of HIV infected individuals. In the latter application, it is particularly desirable to measure absolute number per unit blood volume of T helper lymphocytes, as well as the relative number of such cells within total lymphocytes. These are challenging measurements by immunophenotyping because the characteristic cell surface markers of such cells are shared to varying degrees with non-lymphocyte white blood cells. Consequently, most current approaches for identifying lymphocyte populations require the measurement of at least one cellular property, such as forward or side light scatter when a flow system is employed, in addition to measurements based on cell surface markers.
It would be highly advantageous, particularly for low-cost point-of-care applications, if there were available methods and compositions for analyzing white blood cells, particularly lymphocytes, and their respective subsets solely on the basis of cell surface markers.